Open AccessOrganization of chromosome fibrils in Euglena gracilis
Author(s) -
HAAPALA O. K.,
SOYER MARIEODILE
Publication year - 1975
Publication title -
hereditas
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.819
H-Index - 50
eISSN - 1601-5223
pISSN - 0018-0661
DOI - 10.1111/j.1601-5223.1975.tb01518.x
Subject(s) - fibril , chromosome , biology , electron micrographs , electron microscope , euglena , chromatid , biophysics , crystallography , genetics , optics , chemistry , gene , chloroplast , physics
Euglena gracilis chromosomes spread on water and studied as whole mounts in the electron microscope were found to have axial fibrils (chromosome axis) and chromomere fibrils, i.e. they display essentially the same chromomere organization which has been demonstrated in the chromosomes of higher eukaryotyes. The diameter of chromomere fibrils was about 100 Å but in addition, they appeared to be composed of spheroid subunits about 100–120 Å in diameter. In spread chromosomes the chromomere fibrils of a chromosome often became totally detached from the axis, but at the same time, axial tips (“telomeres”) were found to be in direct continuity with the chromomere fibrils. Thus as a tentative model we suggest that Euglena chromosomes are circular uninemic structures formed by two segments of the unineme: the axis and the chromomere fibril. We also suggest that during evolution of eukaryote chromosome organization chromosomal DNA has remained circular and incidentally that all the chromosomes might be circular structures in which genetic linearity is withheld by interspersion of stretches of axial fibril.